1. Field of the Invention
The present invention relates to a process for the resolution of racemic 3-amino-pentanenitrile with obtainment of enantiomerically enriched 3-aminopentanenitrile or its salts by reaction of racemic 3-aminopentanenitrile with enantiomerically enriched organic acids.
2. Brief Description of the Prior Art
(R)-3-Aminopentanenitrile and its salts are important starting materials for the synthesis of pharmaceutical active compounds. Since the pharmaceutical action is often attributed to only one isomer, it is desirable to prepare or to make available this desired enantiomer in high optical purity. The aim is therefore to plan the synthesis such that racemic intermediate compounds are separated into their enantiomers, in order to obtain homochiral products.
In U.S. Pat. No. 4,260,556, the preparation of racemic 3-aminopentanenitrile by reaction of 2-pentenenitrile with ammonia in the presence of a metallic catalyst is described.
In U.S. Pat No. 4,496,474, the reaction of 2-pentenenitrile with alkylamines with the formation of the corresponding racemic cyano compounds is disclosed. In EP-A0 449 297, an improved variant of this basic reaction of 2-pentenenitrile with alkylamines in the presence of 15–60% by weight of water is described.
U.S. Pat. No. 5,902,883 describes a process for the cyanobutylation of ammonia, alkylamines or hydrazine with 3- and 4-pentenenitrile, or mixtures thereof, with formation of the racemic alkylaminonitriles.
In the aforementioned prior art, no indication at all of a separation of the racemic mixtures obtained in each case is given.
In J. Nat. Prod. 65 (2002), 29–31, the preparation of enantiomerically pure (R)- and (S)-3-aminopentanenitrile by constructive synthesis starting from (R)- or (S)-2-amino-butanol is described.
The preparation of enantiomerically pure or enantiomerically enriched (R)- or (S)-3-aminopentanenitrile by resolution of racemic 3-aminopentanenitrile has hitherto not been described anywhere in the prior art.
Since the only method for the synthesis of enantiomerically enriched 3-amino-pentanenitrile, known from J. Nat. Prod. 65 (2002), 29–31, is very laborious, the object of the present invention consisted in making available a suitable process for the resolution of racemic 3-aminopentanenitrile with enrichment of one of the two enantiomers.